SINGAPORE: For the second time in less than a week, operations at Changi Airport have been disrupted because of unauthorised drone activity in the area.

The Civil Aviation Authority of Singapore (CAAS) said that approximately 15 departures and three arrivals were delayed on Monday (Jun 24), while seven flights were diverted. Bad weather was also a factor in the disruptions.

Monday's incident comes just days after 38 flights were affected when Changi Airport was forced to intermittently close one runway because of drone sightings in the vicinity.

Investigations into both incidents are continuing.

With potentially dangerous and illegal drone flights taking place in many countries, governments have been exploring a range of options to ensure that such incidents - whether malicious or accidental - can be dealt with quickly and efficiently.

1. THE DRONE DOME

At the end of last year, operations at London's Gatwick Airport came to a standstill when multiple reports of drone sightings grounded all flights. Hundreds of thousands of people had their travel plans disrupted as the authorities scrambled to find a way to stop the drone incursions. Commercially available equipment did not help.

In the end, the military was called in, with the British Army reported to have deployed the Israeli-developed Drone Dome. The system uses radar and laser technology to locate drones, and then jams the radio signal between the user and the device, rendering it useless.

Investigations have yet to find out who was responsible for the drone flights.

2. LASER SHOT

The US military is reported to be testing a prototype laser weapon to counter the threat from enemy drones.

The Compact Laser Weapons System - or CLaWS - is the first ground-based laser approved for use by US ground troops, Defense News reported on Friday.

A number of countries and manufacturers are developing or deploying systems that use lasers to disable drones. For instance, the Silent Hunter is an anti-drone laser weapon developed in China by Poly Technologies that was deployed in 2016 at the G20 Summit in Hangzhou.

3. EAGLE HUNTER

In a radical approach, police in the Netherlands experimented with eagles as a way of bringing down drones being flown illegally.

After a series of tests in 2015, the Dutch police said they were putting into operation a flock of the birds of prey to take down drones believed to be posing a danger to the public, such as near airports. The birds had been purchased as chicks and trained by a specialist company Guard From Above.

The experiment was short-lived as the eagles did not always do what they had been trained to do, and the initiative was grounded in 2017.

4. USE A DRONE TO CATCH A DRONE

DroneCatcher is a drone armed with a net gun developed by Delft Dynamics. Once the rogue drone has been detected, DroneCatcher is able to quickly approach hovering or moving threats.

The company claims that with the use of multiple onboard sensors, the net gun can be locked on the target and then launched. After the catch, DroneCatcher can carry the captured drone on a cable to a harmless place and release it there. If the caught drone is too heavy to be carried, it can be dropped with a parachute to ensure low impact on the ground.

The SkyWall 100 also uses a net to catch errant drones - in this case, from a shoulder-mounted cannon.

5. GUNNED DOWN

DroneShield uses a gun to bring down a rogue drone in the final stage of its protection system.

In the initial phase, it uses multi-sensor technologies that work together to detect drones, with radar sensors tracking a moving object, separating it from the background clutter such as trees or birds. Further identification comes with cameras and thermal sensors, allowing for a visual confirmation to the user.

Once detected, a gun is used to send radio-jamming signals and frequencies to disrupt the errant drone's flight.